turned off they homed in on a good-sized blob on the scope. When they turned on the lights, they were surrounded by thousands and thousands of lantern fish. The fish were pointed and moving in all directions—"a fantastic aggregation not a school." The biologists had thought that photophores, which were usually on the underside of the fish, were meant to shine down and blind predators. But the photophores of these lantern fish were aimed in every conceivable direction. Rarely had their nets captured a lantern fish; and yet Alvin's net brought up 744 of them on one dive. Small collecting nets mounted on Alvin were also successfully used near the bottom by Woods Hole biologist George Grice, who discovered 18 new species of copepods on one dive.
While benthic biologists took advantage of Alvin's ability to carry out difficult manipulative tasks in the deep sea, marine geologists took advantage of its high maneuverability. K.O. Emery and a geology group he had formed at Woods Hole began using Alvin to explore the submarine canyons off the Northeast coast. Here a great series of canyons cut across an extensive continental shelf. But geologists were not only interested in understanding the origin of submarine canyons and the role they played in transporting sediments across the continental shelf to the deep sea, these canyons also provided them with knowledge about Earth's recent history.
The continental shelf in most parts of the world consists of horizontal layers of sedimentary rock laid down one layer on top of another over millions of years. As submarine canyons form, they cut down into these layers, exposing in their walls the geochronology or geologic history of the region. Using the submersible's ability to maneuver, geologists were able to sample these outcrops and add further detail to the recent stratigraphic history of the continental shelf.
Similar investigations were carried out in the Straits of Florida and the Bahama Banks, as well as submerged terraces such as the Blake Plateau. Instead of studying sedimentary layers of rock deposited by river outflow, geologists were able to investigate layer upon layer of limestone formed in place by coral growth and erosion.
But submarine canyons and steep vertical scarps were not the only geologic features on the continental margins explored in the 1960s using manned submersibles. A popular winter diving area for Alvin was the Tongue of the Ocean between New Providence and Andros Islands in the Bahamas. The vertical walls of this 2000-m trough consists of fossiliferous limestone providing geologists with the opportunity to look back into the early carbonate geology of this region.
In addition to using Alvin to study the natural history beneath the sea, in one case it was used to investigate human activity on the continental shelf during the Ice Age. Of particular interest was the work dealing with submerged shorelines by K.O. Emery, Robert McMaster, and Richard Edwards. The Ice Age led to the dramatic lowering of sea level on a worldwide basis: 15,000 years ago, off the East Coast of the United States, it was between 70 and 130 meters below its present position.
As sea level rose with the melting of the continental ice sheets, a series of ancient shorelines was created and later flooded, forming relic features on the present continental shelf. During an Alvin dive in 1967, Edwards and Emery encountered a submerged beach and oyster reef formed 8,000 to 10,000 years ago off Chesapeake Bay. On the ridge top inland from the submerged beach they found oyster shells thought to be kitchen middens created by the early humans that must have inhabited this area at the time. Although little has been done since, the continental shelves of the world may prove to contain significant archaeological sites awaiting future discovery.
Just as the scientific community was gaining confidence in Alvin's ability to dive routinely and safely, disaster struck. At the end of its 1968 dive season, Alvin was in the process of being launched on dive 307 when suddenly its forward cables broke, dropping the submersible into the sea. Quick action saved the crew and passenger, but Alvin disappeared beneath the waves, falling 1,585 m to the ocean floor. There it remained until 1969 when a heroic salvage operation returned it to Woods Hole.
As engineers accessed the damage done during her 10 months underwater a startling discovery was made (Jannasch and Wissen, 1970).
Alvin broke surface again in September 1969 after resting almost one year on the ocean floor. In the excitement over her successful recovery, the oceanographers almost overlooked the striking outcome of Alvin degradation experiment: the food in the box lunch was practically untouched by decay, although containing the usual amount of bacteria.
The broth, although being the most perishable material. was perfectly palatable. Four of us are living proof of this fact. The apples exhibited a pickled appearance. But the way the salt water had penetrated into the fruit tissue indicated that the membrane functions were hardly affected. Enzymes were still active, and the acidity of the fruit juice was not different from that of a fresh apple. The bread and meat appeared almost fresh except for being soaked with seawater.
In conclusion, the food recovered from Alvin after ten months of exposure to deep-sea conditions exhibited a degree of preservation that, in the case of fruit, equaled that of careful storage, and in the case of starches and proteins appeared to surpass by far that of normal refrigeration.
The ocean floor as a giant refrigerator was an image that continued to be reinforced as the deep sea began to yield more and more of its preserved human history. The same year that Alvin was lost, she dove on a World War II Hellcat fighter plane that was ditched by its pilot in 1944. Resting in 1,524 m of water, it was in excellent condition.
In marked contrast to these images of a frozen deep ocean setting in which biological processes move at a snail's pace is the work by Dr. Ruth Turner of Harvard's Museum of Comparative Zoology. In 1972, Dr. Turner used Alvin to